Method for load control, and radio system

ABSTRACT

The invention relates to a method for load control and a radio system. In the invention a load result describing the load is cell-specifically formed. The load result is formed either by comparing a signal strength of desired signals ( 23 ) and a combined total strength of interferences ( 13 ) and the desired signals ( 23 ) or by weighting a signal-to-interference ration with a bandwidth or a data transmission rate. The load result is compared with a threshold value of the highest load level allowed of a cell ( 1 ). The data transmission rate in the cell ( 1 ) is increased if the load result is smaller than the threshold value. The data transmission rate in the cell ( 1 ) is reduced and the establishment of new connections is avoided if the load result exceeds the threshold value. In heavy load situations a signal-to-interference objective is also changed in order to balance the load result.

FIELD OF THE INVENTION

The invention relates to a method for load control, the method beingused in a radio system comprising at least one base station and asubscriber terminal which communicate with each other by transmittingand receiving signals representing desired signals and interferences.

The invention further relates to a method for load control, the methodbeing used in a digital radio system comprising at least one basestation and a subscriber terminal which communicate with each other bytransmitting and receiving signals which are desired signals and/orinterferences.

The invention also relates to a radio system comprising at least onebase station and a subscriber terminal which comprise at least onetransceiver and which are arranged to communicate with one another bytransmitting and receiving signals which are desired signals and/orinterferences.

The invention further relates to a radio system comprising at least onebase station and a subscriber terminal which comprise at least onetransceiver and which are arranged to communicate with one another bytransmitting and receiving signals which are desired signals and/orinterferences.

BACKGROUND OF THE INVENTION

The invention is applied to interference limited cellular radio systemsand particularly to a CDMA system. In the CDMA technique the user'snarrowband data signal is modulated by a spreading code, which is morewideband than the data signal, to a comparatively wide band. In themethods, bandwidths from 1 to 50 MHz have been used. The spreading codeis conventionally formed of a long pseudorandom bit sequence. The bitrate of the spreading code is much higher than that of the data signal.In order to distinguish spreading code bits from data bits and symbols,they are called chips. Each user data symbol is multiplied by thespreading code chips. Then the narrowband data signal spreads to thefrequency band used by the spreading code. Each user has his/her ownspreading code. Several users transmit simultaneously on the samefrequency band and the data signals are distinguished from one anotherin the receivers on the basis of a pseudo-random spreading code.

The capacity of interference limited multiple access systems such as theCDMA cellular radio system is determined by an interference power causedby users. In such a system the subscriber terminal usually establishes aconnection with the base station to which the path loss is the smallest.The base station coverage does not in all situations correspond to thetraffic need, but the load of some base stations increases to such anextent that the connections to the subscriber terminals can bedisconnected either due to the increased interference or to theinadequacy of the shift capacity.

It is assumed in prior art handover and power regulation algorithms thata connection is established with the base station to which the path lossis the smallest. Such a best connection principle is thus preferable, asthe traffic load towards the base station is constant or when thesignal-to-interference ratio of the most loaded base station meets theminimum requirement. But when the load of a base station increases tosuch an extent that the minimum requirements of the connection qualitycannot be met, a way is needed to balance the load. A prior art radiosystem does not, however, allow load management that balances the load,but prior art systems easily lead to an unstable situation, in whichdisconnecting the connection to some subscriber terminals is the onlypossibility. Such heavy load situations, in which the connection qualitydeclines below the minimum requirements and which can thus be calledoverload situations, are-not desired.

In the interference limited radio systems it is of primary importance tokeep the load sufficiently low, because otherwise owing to fast powercontrol the transmitters increase their power to the maximum. At worstthis, in turn, could lead to the disconnecting of most radio systemconnections. Then again, it is appropriate to handle simultaneously asmany connections as possible.

SUMMARY OF THE INVENTION

An object of the present invention is to implement a method and a radiosystem applying the method, in which a load can be optimally controlledat a connection and/or cell level, and thus prevent overload situationsand improve the connection quality in a normal situation. Another objectof the invention is also to enable large data transmissions using thehighest possible data rate.

This is achieved with the method of the type set forth in the preamblecharacterized by forming a combined signal strength of one or moredesired signals; forming a combined total strength of the interferencesand one or more desired signals; forming a load result measuring theload by comparing the signal strength and the total strength; comparingthe load result with a threshold value, which is a predetermined measurefor the highest load level allowed, whereby, when the load result andthe threshold value substantially differ from one another, the load isbalanced by changing the telecommunication rate.

The method of the invention is further characterized by formingsignal-specifically one or more desired signal-to-interference ratios;forming a combined load result of the signals by proportioning one ormore desired signal-to-interference ratios with corresponding signalbandwidths and data transmission rates; comparing the load result with athreshold value, which is a predetermined measure for the highest loadlevel allowed, whereby, when the load result and the threshold resultsubstantially differ from one another, the load is balanced by changingthe telecommunication rate.

The radio system of the invention is characterized by comprising signalmeans to form a signal strength of one or more desired signals; totalstrength means to form a combined total strength for both interferencesand one or more desired signals; comparing means to form a load resultby comparing the signal strength and the total strength; threshold meansto compare the load result with a threshold value, which is apredetermined measure for the highest load level allowed, and when theload result and the threshold value substantially differ from oneanother on the basis of the comparison, the radio system is arranged tobalance the load by changing the telecommunication rate.

The radio system of the invention is further characterized by comprisingsignal-to-interference ratio means in which one or more desiredsignal-to-interference ratios are signal-specifically stored; frequencyband means in which information on a bandwidth of one or more signals isstored; data transmission rate means which are arranged to forminformation on a data transmission rate of one or more signals;multiplication means which are arranged to form a load result byproportioning said desired signal-to-interference ratio with said signalbandwidth and data transmission rate; threshold means to compare theload result with a threshold value, which is a predetermined measure forthe highest load result allowed, and when the load result and thresholdvalue substantially differ from one another on the basis of thecomparison, the radio system is arranged to balance the load by changingthe telecommunication rate.

Great advantages are achieved with the method of the invention. Theoverload situations of an interference limited radio system can beavoided and the load can be optimally controlled. In addition, unstablesituations and connection cut-offs can be avoided at the same time as amaximum bit rate can be used in relation to each situation.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail withreference to examples in the accompanying drawings, in which

FIG. 1 shows communication between two transceivers,

FIG. 2 shows a cellular radio system,

FIG. 3 shows a transceiver and

FIG. 4 shows a second transceiver solution of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The method of the invention can be applied to interference limited radiosystems such as a CDMA system without restricting thereto.

Let us now examine in more detail the theoretical basis of theinvention. In the CDMA system a signal-to-interference ratio SIR can bedetermined for each connection i as follows: $\begin{matrix}{{{SIR}_{i} = {P_{{gain},\quad i}\frac{P_{{rx},\quad i}}{P_{{int},\quad i}}}},} & (1)\end{matrix}$

where i is a connection index, P_(rx, i) is a combined strength for areceived desired signal and an interfering signal, P_(int, i), is atotal interference strength and gain P_(gain, i) is defined${P_{{gain},\quad i} = \frac{BW}{DS}},$

where BW is a bandwidth and DS is a data transmission rate. Each signalis both a possible desired signal and an interfering signal, since thesignals interfere with one another. A signal strength is preferablymeasured as a signal power without restricting thereto, since thesolution of the invention also operates by applying another parameterdescribing the signal strength. The data transmission rate DS ismeasured, for example, as bits per second. The bandwidth BW is thebandwidth the receiver employs for a radio-frequency signal. What ismeant by a connection is the connection between a subscriber terminaland a base station, the connection usually being established for a callor a data transmission. In a typical radio system the subscriberterminal is preferably a mobile phone.

When P_(gain, i) in formula (1) is divided into the left side of theformula and a sum of a signal and an interference of all connections iis formed, and $\begin{matrix}{{L = {{\sum\limits_{i}\quad \frac{{SIR}_{i}}{P_{{gain},\quad i}}} = {\sum\limits_{i}\quad \frac{P_{{rx},\quad i}}{P_{{int},\quad i}}}}},} & (2)\end{matrix}$

is obtained, where L is a load. In the CDMA system a total interferenceis formed from other signals than precisely the desired signal (desiredsignals) and from a constant interference caused by otherelectromagnetic radiation on said frequency band and, for example, fromthe transceiver's thermal noise. The desired signal means the receivedsignal which is to be detected. Other signals cause interference and arethus interferences. In this way formula (2) can be converted into mode:$\begin{matrix}{{L = {{\sum\limits_{i}\quad \frac{{SIR}_{i}}{P_{{gain},\quad i}}} = {{\sum\limits_{i}\quad \frac{P_{{rx},\quad i}}{P_{{int},\quad i}}} = \frac{\sum\limits_{i}\quad P_{{rx},\quad i}}{{\sum\limits_{i}\quad P_{{rx},\quad i}} + I}}}},} & (3)\end{matrix}$

where$\left. \frac{\sum\limits_{i}\quad P_{{rx},\quad i}}{{\sum\limits_{i}\quad P_{{rx},\quad i}} + I}\rightarrow 1 \right.,\left. {{when}\quad {\sum\limits_{i}\quad P_{{rx},\quad i}}}\rightarrow{\infty.} \right.$

In formula (3) I is a total interference comprising the receiver'snoise, pilot signal interferences and the interference caused by othercells. P_(rx) ja I depend upon each other to the effect that, whentransmitted powers are increased in order to enlarge power P_(rx),several parts of interference I also increase, as the signals of P_(rx)interfere, for example, with the neighbouring cell in which the powersto be used are increased. Formula (3) shows that irrespective of howhigh the strength of the received signal$\sum\limits_{i}\quad P_{{rx},\quad i}$

grows, the left side of formula (2) stays smaller than 1. The results offormula (3) are directly valid at an antenna but the results have to beproportioned to the efficiency of interference cancellation when IC orMUD (Interference Cancellation, Multi-User Detection) methods are usedin reception, as interference cancellation reduces the mutualinterference of the signals. If, for example, the MUD method reducesinterference to a fifth, the limit value becomes fivefold, or 5. Basedon this information the solutions of the invention can be implemented.The closer the value 1 the result of formula (2) is, the higher the loadL of the receiver is. It is not worthwhile to let the load L grow toohigh, instead it should be aimed to keep the load L sufficiently belowthe threshold value result 1.

Let us now examine in greater detail the method of the inventionutilizing FIGS. 1 and 2. The situation in FIG. 1 comprises transceivers10 and 11, a bi-directional communication with a desired signal 12 andinterferences 13. The transceiver 10 is, for example, a base station andthe transceiver 11 is a subscriber terminal. When the subscriberterminal 11 transmits 10 its own signal 12, or the desired signal, tothe base station 10, the base station 10 receives the desired signal 12,but simultaneously the base station 10 receives the interferences 13,which interfere with the detection of the desired signal 12. In order toimprove the quality of the desired signal 12 and to ensure thedetection, the base station 10 transmits a command to the subscriberterminal 11 concerning the change of the data transmission rate. As theinterferences 13 interfere with the connection 12 the command preferablycomprises information on reducing the data transmission rate. Afteracknowledging the command both the base station 10 and the subscriberterminal 11 use the reduced data transmission rate, which improve theinterference tolerance of both receivers 10 and 11.

The method of the invention thus operates in more general terms asfollows. A signal strength P_(rx) of one or more desired signals 12 isformed and similarly a combined total strength P_(rx) +I of theinterferences 13 and the de sired signal 12 is also formed. By comparingthe signal strength P_(rx) to the total strength P_(rx) +I, whereby aload result L is formed, and by further comparing the load result thusformed to a predetermined threshold value K_(t), or to the load goal,measures are taken, if required, to balance the load. The comparison canbe performed, for example, by dividing or calculating the difference. Ifthe load L is substantially more than what is allowed according to thethreshold value K_(t), or in accordance with formula (3) $\begin{matrix}{{L = {\frac{\sum\limits_{i}\quad P_{{rx},\quad i}}{{\sum\limits_{i}\quad P_{{rx},\quad i}} + I} > K_{t}}},} & (4)\end{matrix}$

where K_(t) is a predetermined threshold value, the load L is reducedpreferably by decreasing the data transmission rate of the desiredsignal. If again the load L is substantially less than what is allowedby the threshold value K_(t), or according to formula (3)$\begin{matrix}{{L = {\frac{\sum\limits_{i}\quad P_{{rx},\quad i}}{{\sum\limits_{i}\quad P_{{rx},\quad i}} + I} < K_{t}}},} & (5)\end{matrix}$

the data transmission rate of the desired signal 12, or generally of anysignal, can be increased. Thus, according to the method of theinvention, which can particularly be applied to the base station, theload L is kept constant.

FIG. 2 illustrates the solution of the invention in a cellular radiosystem. The cellular radio system comprises cells 1 and 2. The cell 1comprises a base station 20 and subscriber terminals 21 and 22. Thesubscriber terminals 21 and 22 are preferably mobile phones. Thesubscriber terminals 21 communicate with the base station 20 in the cell1 The subscriber terminal 22 does not communicate with anything in thesituation of this example. The desired signals of the cell 1 are signals23 as they represent traffic within the cell 1. The same signals 23 alsorepresent interference within the cell as the desired signals 23interfere with one another. Signals of other cells arrive at the cell 1from outside, the signals being interferences 13 in the cell 1. In thecell 1 interferences I are also represented by other electromagneticradiation on the frequency band of the desired signals interfering withthe desired signals 23 and by the noise of the receiver. In the methodof the invention the relations between the interferences 13 and 23 andthe desired signals 23 are to be kept in balance and the threshold valueK_(t) of the relation between the interferences 13 and the desiredsignals 23 is to be predetermined, on the basis of which threshold valuethe data transmission rate of the desired signals is either increased orreduced. Then the load L of the receiver increases or decreases. In thecell 1 the combined signal strength P_(rx) of the desired signals 23 issummed or otherwise correspondingly formed. Furthermore, the combinedtotal strength P_(rx) +I of the interferences 13 and the desired signals23 is similarly formed. By comparing the signal strength Pri to thetotal strength P_(rx) +I, whereby the load result L is obtained, and byfurther comparing the load result L thus formed to the predeterminedthreshold value k measures are taken, if required, in the cell 1 tobalance the load L. The comparison can be performed, for example, bydividing or calculating the difference. If the load L substantiallyexceeds what is allowed according to the threshold value K_(t) inaccordance with formula (4), the effect of the interferences 13 and 23on the desired signals 23 of the cell is reduced preferably bydecreasing the data transmission rate of the desired signals 23. At thistime new connections are not preferably established either, before theload situation has changed in such a way that there is less load L thanwhat is allowed according to the threshold value K_(t), since the newconnections would further increase the load.

If again the load L is substantially less than what is allowed accordingto the threshold value K_(t) in accordance with formula (5), the datatransmission rate of the desired signals 23 can be increased. Therelation between the strengths P_(rx) of the desired signals 23 and thecombined strengths P_(rx) +I of both the interferences 13 and thedesired signals 23 is aimed to keep constantly stable in the cell 1.

In the second method of the invention the effect of the datatransmission rate change on the load L can more clearly be concluded. Inthis method a signal-to-interference ratio SIR_(i) of each connection iis given a connection-specific desired value SIR_(i,t) in formula (3)and in order to calculate the load L it is proportioned by the bandwidthBW and the data transmission rate DS. Thus, the aim is to keep formula(6) continuously valid for the connections $\begin{matrix}{{{L \leq {\sum\limits_{i}\quad {{DS}_{i}*\frac{{SIR}_{i,t}}{BW}}}} = {{1 - ɛ} = K_{t}}},} & (6)\end{matrix}$

where 1−ε is a load objective, or a threshold value load K_(t),. Theload situation is most preferable when the load L corresponds to thedesired threshold value K_(t), whereby L =K_(t). Thesignal-to-interference ratio SIR_(i,t) is preferably formed usingfiltering to the effect that it is a moving average value of themeasured signal-to-interference ratios SIR, for example, a mean. SinceSIR_(i,t) changes slowly, by changing the data transmission rate in avariable P_(gain,i) the load L also changes in an easily predictableway. The parameter ε can be constant or variable and its value should bebetween FIGS. 0 and 1. Typically the value of the parameter ε can be,for example, 0.5. The value of the desired signal-to-interference ratioSIR_(i,t) thus depends on the connection i and the cell and thereforethe value of SIR_(i,t) has to be adapted according to the situation. Forexample, the base station preferably measures, when operating, thesignal-to-interference ratios SIR repeatedly. Then the load result L isregularly formed, for example, at 20 ms intervals. A bit-error-rate BER,a signal-to-noise ratio S/N or equivalent can be used as a measure ofthe signal-to-interference ratio SIR in the solution of the invention.

The strengths of the signals and interferences can be determined in themethod of the invention from the signals' instantaneous or long-termstatistical effective values or from other equivalent values. In themethod of the invention the data transmission rate is reduced preferablyin the connections that have the highest energy per transmitted symbol,or usually per bit. This facilitates the detection in difficultcircumstances. The data transmission rate is, in turn, increasedcell-specifically preferably in the connections that have the smallestenergy per transmitted symbol, or usually per bit. Thus, an optimallyfast data transmission rate is obtained in respect of the interferences.

As SIR_(i) , also represents, for example, in formula (6) a signalinterference objective aimed at, in addition to changing the datatransmission rate in the method of the invention the load can bebalanced also by changing the signal-to-interference ratio SIR_(i)objective. Such an operation is advantageous, for example, in heavilyloaded circumstances, when more interference has to be accepted thanusually.

In addition to changing the data transmission rate and thesignal-to-interference ratio objectives, the establishment of newconnections is also controlled in the inventive method. Then a newconnection to be established particularly increases the load of the basestation, hence the new connection is allowed to be established in themethod of the invention only if the load L remains smaller than thehighest possible load.

Let us now examine in more detail the establishment of the newconnection in an up-link direction in a typical radio system. The basestation calculates an up-link load L_(up) using formula (6). The basestation also calculates an estimated load situation L_(new,up) for thenew connection $\begin{matrix}{{L_{{new},\quad {up}} = {L_{up} + {{Ds}_{i}*\frac{{SIR}_{t,\quad {up}}}{BW}}}},} & (7)\end{matrix}$

The base station also calculates continuously, regularly or irregularlya standard deviation, a variance or equivalent std_(L) of the load L,which it utilizes when forming the threshold value K_(t) of the load.The threshold value K_(t) of the load is of the same kind in formulas(4) and (5) but the effect of uncontrolled new connections on the loadsituation is preferably also taken into account. If an estimated loadL_(new, up) is smaller than a threshold value K_(t) a connection can beestablished. Otherwise a new connection is not established. In otherwords, when formula (8) is valid the connection is established:

L_(new,up)<K_(t)=1−ε−M * std_(L)+margin_(ho),  (8)

where M is a freely chosen parameter (typically M =5) and margins, is ahandover parameter (typically 0.05 when handover is performed, 0 for anew beginning connection), which is meant to prioritize a new handoverconnection. The load of uncontrolled connections can be taken intoaccount by reducing the threshold value K_(t) by an amount based onstandard deviation std_(L), and thus aiming to leave reserve space for anew connection.

In a down-link direction the establishment of a connection is controlledsimilarly as in the up-link direction. If the estimated load L_(new, up)is smaller than the threshold value K_(t), the connection can beestablished. Otherwise a new connection is not established. In otherwords, when formula (8) is valid the connection is established. Inaddition, the total strength P_(tot) of the signal transmitted by thebase station preferably has to be smaller than the threshold valueP_(th) of the strength. The total value P_(tot) of the strengthcomprises at least a real desired signal strength P_(s) and preferablyalso a pilot signal strength P_(p) associated with the desired signal.In formula mode this can be shown as follows:P_(th)>P_(s)+P_(p)=P_(tot). The strengths of the desired signal and thepilot signal are preferably effective values.

FIG. 3 illustrates the solution of the invention which can preferably belocated at the base station and the base station controller of the radiosystem. The transceiver comprises an antenna 40, signal pre-processingmeans 41, post-processing means 42, signal means 43, total strengthmeans 44, comparing means 45, threshold means 46, control means 47,transmission means 48, threshold value means 53, in which a thresholdvalue is stored, means 54 to calculate standard deviation, means 55 toprioritize the subscriber terminal performing handover,signal-to-interference ratio means 60 and measuring means for totalsignal strength 64. The radio-frequency transmission received by theantenna 40 typically comprises signals from various transmitters whichfunction as sources for both the desired signals 23 and theinterferences 13. The combined signal combination of the interferences13 and the desired signals 23 propagates from the antenna 40 to thepre-processing means 41 comprising, for example, radio frequency meansand a filter (not shown in the Figure). The radio frequency means andthe filter calculate the frequency of the received signal combinationpreferably for the intermediate frequency. The signal combination canalso be handled by the pre-processing means 41 analogically and/ordigitally. The post-processing means 42 comprise signal processing meanswhich are needed, for example, at the base station of the radio system,but the function or structure of the post-processing means 42 is notimportant in terms of the invention.

The substantial structures concerning the invention are means 43-45which implement the method of the invention. A combined signal strength50 of the desired signals 23 of the cell 1 is formed in the signal means43. A total strength 51 of both the desired signals and theinterferences 13 is formed in the total strength means 44. Byproportioning the strengths to one another to a load result 52 in themeans 45 and by comparing the result 52 to a predetermined thresholdvalue 53 in threshold means 46, the threshold means 46 can informcontrol means 47 whether a change in data transmission rate is needed.The control means 47 transmit, if necessary, in connection with thechange command of the data transmission rate to other parties involved(subscriber terminals) by transferring the change command to a modulator48 and onwards to the antenna 40. The control means 47 can also changethe transmitter's transmission rate by controlling the transmissionmodulator 48 to the effect that the data transmission rate changes.Using means 54 and 55 the magnitude of a threshold value 53 is changedaccording to the method of the invention. Means 40, 41, 42, 43, 44, 48and 64 are conventionally located at the subscriber terminal or the basestation. Means 45 and 60 are usually located at the base station andmeans 46, 47, 53, 54 and 55 are usually located at the base station orthe base station controller. However, the location is un-essential forthe invention.

FIG. 4 shows a block diagram which implements the solution of theinvention somewhat differently than the solution in FIG. 3. The solutioncomprises an antenna 40, preprocessing means 41, post-processing means42, signal-to-interference ratio means 60, frequency band means 61, datatransmission rate means 62, multiplication means 63, measuring means fortotal signal strength 64, threshold means 46, control means 47,transmission means 48 and threshold value means 53 in which a thresholdvalue is stored. The solution functions in other respects substantiallysimilarly as the solution in FIG. 3, but regarding the means 60-63 thefunction is different. The signal-to-interference ratio means 60 forms asignal-to-interference ratio 70 being the objective and applicable tothe operational circumstances. The signal-to-interference ratio 70 issignalled onwards to means 54 and 63. The frequency band means 61possesses information on a bandwidth BW 71 used. The signal bandwidth istypically predetermined. Information on a signal data transmission DS 72is formed, or it is stored in the means 62. The data transmission rateis typically predetermined but can also be detected from the signal bymeasuring in the data transmission rate means 62. In the multiplicationmeans 63 the signal-to-interference ratio 70 is proportioned, forexample, in accordance with formula (2) by the bandwidth 71 (BW) and thedata transmission rate 72 (DS) to a load result 52 and by comparing theresult 52 with the pre-determined threshold value 53 in the thresholdmeans 46, the threshold means 46 can inform the control means 47 whetherthe data transmission needs to be changed. Using means 54 and 55 themagnitude of the threshold value 53 is changed according to the methodof the invention. In a conventional solution means 40, 41, 42, 47, 48,60 and 64 are located at the subscriber terminal or the base station.Means 46, 53, 54, 55 and 63 are located at the base station and/or thebase station controller. The location of means 61 and 62 can in aconventional solution vary, and be at the subscriber terminal, the basestation and the base station controller. However, the location is notessential for the invention.

The solutions of the invention can be implemented particularly regardingdigital signal processing, for example, with ASIC or VLSI circuits. Thefunctions to be performed are preferably implemented as programs basedon microprocessor technology.

Even though the invention has above been described with reference to theexample of the accompanying drawings, it is obvious that the inventionis not restricted to it but can be modified in various ways within thescope of the inventive idea disclosed in the attached claims.

What is claimed is:
 1. A method for load control, the method being usedin a digital radio system comprising at least one base station (20) anda subscriber terminal (21 and 22) which communicate with each other bytransmitting and receiving signals which are desired signals (23) and/orinterferences (23, 13), characterized by forming signal-specifically oneor more desired signal-to-interference ratios (70); forming a combinedload result (52) of the signals by proportioning one or more desiredsignal-to-interference ratios (70) with corresponding signal bandwidths(71) and data transmission rates (72); comparing the load result (52)with a threshold value (53), which is a predetermined measure for thehighest load level allowed, whereby, when the load result (52) and thethreshold value (53) substantially differ from one another; the load isbalanced by changing the telecommunication rate.
 2. A method as claimedin claim 1, characterized by balancing the load by changing one or moretelecommunication rates and/or signal-to-interference ratios.
 3. Amethod as claimed in claim 1, characterized by forming one or moredesired signal-to-interference ratios (70) as a moving average valuefrom the measured signal-to-interference ratios.
 4. A method as claimedin claim 1 characterized by reducing the data transmission rate when theload result (52) is substantially higher than the threshold value (53);or increasing the data transmission rate when the load result (52) issubstantially smaller than the threshold value (53).
 5. A method asclaimed in claim 1, characterized by, when the signals comprise digitalsymbols, reducing the data transmission rate in the connections havingthe highest energy per symbol, and increasing the data transmission ratein the connections having the smallest energy per symbol.
 6. A method asclaimed in claim 1, characterized by, avoiding the establishment of newconnections when the load result (52) is substantially higher than whatis allowed according to the threshold value (53) until the load result(52) is again substantially smaller than the threshold value (53).
 7. Amethod as claimed in claim 6, characterized by forming the load result(52) repeatedly and by reducing the threshold value (53) by a valuebased on a mean deviation (54) of the previous load results (52) whenthe load result (52) is compared with the threshold value (53).
 8. Amethod according to claim 6, characterized by prioritizing a connectionperforming handover by adding a handover parameter (55) to the thresholdvalue (53).
 9. A method as claimed in claim 6, characterized in that abase station (20) comprises measuring means for total signal strength(64) whereby the establishment of a new connection is avoided if thecombined strength of a desired signal (23, 24) and a pilot signal ishigher than a predetermined minimum.
 10. A method as claimed in claim 1,characterized in that when the radio system comprises cells (1) thetelecommunication rates are increased or reduced in the area of eachcell (1) irrespective of one another.
 11. A radio system as claimed inclaim 10, characterized in that when the signals comprise digitalsymbols, the radio system is arranged to reduce the data transmissionrates particularly in the connections having the highest energy persymbol, and that the radio system is arranged to increase the datatransmission rate particularly in the connections having the smallestenergy per symbol.
 12. A radio system as claimed in claim 10,characterized by the radio system being arranged to avoid theestablishment of new connections before the load result (52) is againsubstantially smaller than the threshold value. (53).
 13. A radio systemas claimed in claim 10, characterized in that when the radio systemcomprises cells (1) the radio system is arranged to increase or reducethe data transmission rate separately in the area of each cell (1). 14.A radio system comprising at least one base station (20) and asubscriber terminal (21 and 22) which comprise at least one transceiverand which are arranged to communicate with one another by transmittingand receiving signals which are desired signals (23) and/orinterferences (23, 13), characterized by comprisingsignal-to-interference ratio means (60) in which one or more desiredsignal-to-interference ratios (70) are signal-specifically stored;frequency means (61) in which information on a bandwidth (71) of one ormore signals is stored; data transmission rate means (62) which arearranged to form information on a data transmission rate (72) of one ormore signals; multiplication means (63) which are arranged to form aload result (52) by proporting said desired signal-to-interference ratio(70) with said signal bandwidth (71) and data transmission rate (72);threshold means (46) to compare the load result (52) with a thresholdvalue (53), which is a predetermined measure for the highest load resultallowed, and when the load result (52) and threshold value (53)substantially differ from one another on the basis of the comparison,the ration system is arranged to balance the load by changing thetelecommunication rate.
 15. A radio system as claimed in claim 14,characterized by the radio system being arranged to balance the load bychanging the telecommunication rate and/or the signal-to-interferenceratio when the load result (52) and the threshold value (53)substantially differ from one another on the basis of the comparison.16. A radio system as claimed in claim 14, characterized by the datatransmission rate means (62) being arranged to form one or more desiredsignal-to-interference ratios (70) as a moving average value from themeasured signal-to-interference ratios.
 17. A radio system as claimed inclaim 14, characterized by being arranged to reduce the datatransmission rate when the load result (52) is higher than the thresholdvalue (53); or to increase the data transmission rate when the loadresult (52) is smaller than the threshold value (53).
 18. A radio systemas claimed in claim 17, characterized in that the load result (52) iscontinuously formed and the threshold value (53) is reduced by a valuebased on the mean deviation of the previous load results (52) when theload result (52) is compared with the threshold value (53).
 19. A radiosystem as claimed in claim 17, characterized by being arranged toprioritize a connection performing handover by adding a handoverparameter (55) to the threshold value (53).
 20. A radio system asclaimed in claim 17, characterized in that when a base station (20)comprises a measuring means for total signal strength (64) the radiosystem is arranged to avoid the establishment of a new connection if thecombined strength of a desired signal (23) and a pilot signal is higherthan a predetermined minimum.
 21. A radio system as claimed in claim 14,characterized in that when the signals comprise digital symbols, theradio system is arranged to reduce the data transmission ratesparticularly in the connections having the highest energy per symbol,and that the radio system is arranged to increase the data transmissionrate particularly in the connections having the smallest energy persymbol.
 22. A radio system as claimed in claim 14, characterized by theradio system being arranged to avoid the establishment of newconnections before the load result (52) is again substantially smallerthan the threshold value. (53).
 23. A radio system as claimed in claim14, characterized in that when the radio system comprises cells (1) theradio system is arranged to increase or reduce the data transmissionrate separately in the area of each cell (1).